no worries about Shimano parts, they have been tested millions of times. It's the electronics that is not so well tested. Things like battery casing, motor casing, the lugs on the battery cover when you remove the battery, cell welding failure, LCD broken, LCD cable that gets snagged. On my new road bike, there isn't a cable (electric) that is not routed inside.Good point Woosh, we are very mindful of such pitfalls. That's why we are using high end branded parts though-out, such as the Shimano Ultegra R8070 Di2 Disc Groupset which can be bought at just under £1,400.00 from discounters, but retails normally at £2,000 plus. No cheap plastic parts there I trust.